I had a game which I designed using libgdx.
It was displaying ads before publishing it on Google Play as I tested it by this code:
adView = new AdVie
Test Ad working fine but not getting live Ads.
Follow these steps :
Wait for some times/hours.
If you're able to load test ads but not live ads, It sounds like an issue with your AdMob account.
After waiting still having problem then you need to cross check Ad unit Id and AppId from AdMob account.